Update README.md

README.md

@@ -60,7 +60,7 @@ following command
 python -m pip install git+https://github.com/ami-iit/robot-log-visualizer.git
 ```
 
-## 🏃 Example
+## 🏃 Usage
 
 Once you have installed the `robot-log-visualizer` you can run it from the terminal
 
@@ -69,6 +69,28 @@ Once you have installed the `robot-log-visualizer` you can run it from the termi
 You can navigate the dataset thanks to the slider or by pressing `Ctrl-f` and `Ctrl-b` to move
 forward and backward.
 
+### 💡 Environment variables
+`robot-log-visualizer` looks for the model in the folders pointed by one of the following environment variables:
+`GAZEBO_MODEL_PATH`, `ROS_PACKAGE_PATH`, `AMENT_PREFIX_PATH` Please remember to add your model folder to one of these
+environment variables.
+For instance, if you have a model in the folder `~/my-models` you can add it to the `GAZEBO_MODEL_PATH` with the
+following command
+```console
+export GAZEBO_MODEL_PATH=${GAZEBO_MODEL_PATH}:~/my-models
+ ``` 
+Where `~/my-models` is the path to your models folder that is structured as follows
+```console
+tree ~/my-models
+~/my-models
+├── model1
+│   ├── model.config
+│   └── model.urdf
+└── model2
+    ├── model.config
+    └── model.urdf
+```
+And the name of the robot stored in the `mat` file is `model1` or `model2`.
+
 ##  🐛 Bug reports and support
 All types of [issues](https://github.com/ami-iit/robot-log-visualizer/issues/new) are welcome.